Staining of the dorsal root primary afferent fibers by anterograde movement of horseradish peroxidase and retrograde labelling of motoneurons and preganglionic autonomic cells in the turtle spinal cord.

The enzyme horseradish peroxidase (HRP) has been applied to the proximal stumps of severed thoracic and lumbar dorsal roots in the turtles Pseudemys scripta elegans and Testudo hermanni. The results obtained confirm the distribution pattern observed with anterograde degeneration techniques. Primary afferent terminal structures, however, could be demonstrated in more detail. Commonly, ventral roots were also more or less damaged which resulted in the presence of retrogradely labeled motoneurons and small cells in area X. This group of retrogradely labeled small neurons probably represents cells of origin of preganglionic autonomic fibers.